minor error message enhancement in refuseDupeIndexAttach

From 1b9f592756eab51049307862aa6f954e551743ac Mon Sep 17 00:00:00 2001
From: jian he <jian.universality@gmail.com>
Date: Tue, 15 Apr 2025 15:50:08 +0800
Subject: [PATCH v1 1/1] minor error message enhancement

in refuseDupeIndexAttach change it
from
errdetail("Another index is already attached for partition \"%s\"."...)
to
errdetail("Another index \"%s\" is already attached for partition \"%s\".")

So we can easily understand which index is already attached for partition \"%s\".

discussion: https://postgr.es/m/
---
 src/backend/commands/tablecmds.c       | 3 ++-
 src/test/regress/expected/indexing.out | 2 +-
 2 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c
index b3ed69457fc..c113f7e022f 100644
--- a/src/backend/commands/tablecmds.c
+++ b/src/backend/commands/tablecmds.c
@@ -21674,7 +21674,8 @@ refuseDupeIndexAttach(Relation parentIdx, Relation partIdx, Relation partitionTb
 				 errmsg("cannot attach index \"%s\" as a partition of index \"%s\"",
 						RelationGetRelationName(partIdx),
 						RelationGetRelationName(parentIdx)),
-				 errdetail("Another index is already attached for partition \"%s\".",
+				 errdetail("Another index \"%s\" is already attached for partition \"%s\".",
+						   get_rel_name(existingIdx),
 						   RelationGetRelationName(partitionTbl))));
 }
 
diff --git a/src/test/regress/expected/indexing.out b/src/test/regress/expected/indexing.out
index bcf1db11d73..4d29fb85293 100644
--- a/src/test/regress/expected/indexing.out
+++ b/src/test/regress/expected/indexing.out
@@ -248,7 +248,7 @@ alter index idxpart_a_b_idx attach partition idxpart1_a_b_idx; -- quiet
 create index idxpart1_2_a_b on idxpart1 (a, b);
 alter index idxpart_a_b_idx attach partition idxpart1_2_a_b;
 ERROR:  cannot attach index "idxpart1_2_a_b" as a partition of index "idxpart_a_b_idx"
-DETAIL:  Another index is already attached for partition "idxpart1".
+DETAIL:  Another index "idxpart1_a_b_idx" is already attached for partition "idxpart1".
 drop table idxpart;
 -- make sure everything's gone
 select indexrelid::regclass, indrelid::regclass
-- 
2.34.1